1. Field of the Invention
The present invention relates to a photosensitive polymer and a photoresist composition, and more particularly, to a photosensitive polymer having a protecting group including a fused aromatic ring, and a photoresist composition containing the same.
2. Description of the Related Art
As the manufacture of semiconductor devices becomes more complex and current semiconductor chips are more integrated, it is essential to form fine patterns in photolithography. Furthermore, as the capacity of semiconductor devices increases to exceed 1 Gigabit, a pattern size having a design rule less than 0.2 xcexcm is required.
In general, a photosensitive polymer is used as photoresist, which should have characteristics of: (1) high resistance to dry etching, (2) being transparent against a specific wavelength to be used, and (3) excellent adhesion to underlying layers on which patterns are formed.
A conventional photoresist typically has poor resistance to dry etching. After a photoresist pattern is formed on an underlying layer (e.g., a silicon layer) by lithography, the underlying layer is dry etched using a plasma gas. During the dry etching process, the photoresist pattern serves as a mask layer with respect to the underlying layer. As the pattern size becomes smaller, the thickness of the photoresist is gradually decreased. If the photoresist has poor resistance to dry etching, the underlying layer cannot be etched into a desired shape and the critical dimension (CD) of the underlying layer""s pattern is varied. Accordingly, to ensure selectivity of the photoresist layer with respect to the underlying layer during a dry etching process, the photoresist layer must have strong resistance to dry etching.
Accordingly, it would be desirable to develop new photoresist materials having strong resistance to dry etching.
A photosensitive polymer having an acid-labile protecting group is provided. The photosensitive polymer has a general formula as follows: 
wherein the acid-labile protecting group comprises a fused aromatic ring; R1 is hydrogen atom or alkyl group having from 1 to 4 carbon atoms; X is hydrogen atom, halogen, alkyl, or alkoxy; and y is an integer from 1 to 3.
According to an aspect of the invention, the acid-labile protecting group is bound to a polymer backbone of the photosensitive polymer, the polymer backbone of the photosensitive polymer includes acrylate backbone, methacrylate backbone, and norbornene backbone; the fused aromatic ring is a liner ring or branched ring with y greater than or equal to 2; the photosensitive polymers have a weight average molecular weight ranging from about 3,000 to about 200,000.
A photoresist composition is also provided which comprises: (a) a photosensitive polymer having an acid-labile protecting group represented by the formula: 
wherein the acid-labile protecting group comprises a fused aromatic ring; R1 is hydrogen atom or alkyl group having from 1 to 4 carbon atoms; X is hydrogen atom, halogen, alkyl, or alkoxy; and y is an integer from 1 to 3; and (b) a photoacid generator (PAG).
According to an aspect of the invention, the acid-labile protecting group is bound to a polymer backbone of the photosensitive polymer; the fused aromatic ring is a liner ring or a branched ring with y greater than or equal to 2; the photosensitive polymer has a weight average molecular weight ranging from about 3,000 to about 200,000.
According to a preferred aspect of the present invention, the photoresist composition comprises from about 0.5 to about 10 weight percent of the photoacid generator based on the weight of the photosensitive polymer. The photoacid generator is selected from the group consisting of triarylsulfonium salt, diaryliodonium salt, sulfonate, and mixtures thereof.
The photoresist composition further comprises an organic base. The organic base comprises from about 0.5 to about 50 weight percent based on the weight of the photoacid generator. The organic base is selected from the tertiary amine group consisting of triethylamine, triethanolamine, triisobutylamine, triisooctylamine, triisodecylamine, and mixtures thereof.
The preferred embodiments of the present invention will be described more fully hereinafter, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclose will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
The present invention provides photosensitive polymers having an acid-labile protecting group at its polymer backbone, the acid-labile protecting group including a fused aromatic ring having the following formula: 
In the above formula, R1 is hydrogen atom or alkyl group having from 1 to 4 carbon atoms; X is hydrogen atom, halogen, alkyl, or alkoxy; and y is an integer from 1 to 3, wherein the fused aromatic ring is a liner ring or branched ring with y greater than or equal to 2.
The photosensitive polymers of the present invention may have various molecular weights. Preferably, the photosensitive polymers have weight average molecular weight (Mw) of about 3,000 to about 200,000. More preferably, the weight average molecular weights range from about 4,000 to about 50,000.
The backbone of the photosensitive polymers according to the present invention may be varied. Representative examples of the backbone of the photosensitive polymers include acrylate backbone, methacrylate, and norbornene backbones.
According to the present invention, the photosensitive polymer is expressed by the following chemical formula (1): 
In the chemical formula (1), R1 and y are the same as defined above; Z is hydrogen atom or methyl group, and the ratio of m/(m+n) ranges from about 0.05 to about 0.4.
According to the present invention, the photosensitive polymer is expressed by the following chemical formula (2): 
In the chemical formula (2), R1, y, and Z are the same as defined above; Y is hydrogen atom, alkyl, alkoxy, or tert-butoxycarbonyloxyl group; the ratio of l/(l+m+n) ranges from about 0.05 to about 0.4; and the ratio of n/(l+m+n) ranges from about 0.1 to about 0.3.
According to the present invention, the photosensitive polymer is expressed by the following chemical formula (3): 
In the chemical formula (3), R1 and y are the same as defined above; R2 is hydrogen atom, methyl, ethyl, or tert-butyl group; Z1 is hydrogen atom or methyl group; Z2 is hydrogen atom or methyl group; the ratio of l/(l+m+n) ranges from about 0.05 to about 0.4; and the ratio of n/(l+m+n) ranges from about 0.1 to about 0.3.
According to the present invention, the photosensitive polymer is expressed by the following chemical formula (4): 
In the chemical formula (4), R1, y and Z are the same as defined above; the ratio of m/(m+n) ranges from about 0.5 to about 0.7; and the ratio of n/(m+n) ranges from about 0.3 to about 0.5.
According to the present invention, the photosensitive polymer is expressed by the following chemical formula (5): 
In the chemical formula (5), R1, R2, y, Z1, and Z2 are the same as defined above; the ratio of l/(l+m+n) ranges from about 0.3 to about 0.6; the ratio of m/(l+m+n) ranges from about 0.3 to about 0.5; and the ratio of n/(l+m+n) ranges from about 0.1 to about 0.4.
According to the present invention, the photosensitive polymer is expressed by the following chemical formula (6): 
In the chemical formula (6), R1, y, and Z are the same as defined above; R2 is hydrogen atom, hydroxyl, carboxyl, or tert-butyl ester group; the ratio of l/(l+m+n) ranges from about 0.3 to about 0.6; the ratio of m/(l+m+n) ranges from about 0.3 to about 0.5; and the ratio of n/(l+m+n) ranges from about 0.1 to about 0.4.
According to an embodiment of the present invention, the protecting group of the photosensitive polymer includes a variety of fused aromatic rings. Representative examples of the protecting group which can be bound easily to the backbone of the photosensitive polymer have the following chemical formulae 7 through 12: 
In chemical formulae 7 through 11, R is hydrogen atom or alkyl group having from 1 to 4 carbon atoms. The backbone of the photosensitive polymer according to the present invention may be varied. Representative examples of the backbone of the photosensitive polymer include (meth)acrylate and norbornene backbones.
The present invention also provides photoresist compositions. The photoresist compositions comprise: (a) a photosensitive polymer having an acid-labile protecting group at its polymer backbone, wherein the acid-labile protecting group including a fused aromatic ring having the following formula: 
and (b) a photoacid generator (PAG).
In the above formula, R1 is hydrogen atom or alkyl group having from 1 to 4 carbon atoms; X is hydrogen atom, halogen, alkyl, or alkoxy; and y is an integer from 1 to 3, wherein the fused aromatic ring is a liner ring or branched ring with y greater than or equal to 2.
Various photoacid generators may be used in the photoresist compositions. Preferably, the photoacid generators are selected from the group consisting of triarylsulfonium salt, diaryliodonium salt, sulfonate, and mixtures thereof. The photoacid generators may be used in various amounts in the photoresist composition. Preferably, the photoresist compositions include from about 0.5 to about 10 weight percent of the photoacid generators based on the weight of the photosensitive polymer. The photoresist compositions further comprise an organic bases in an amount of from about 0.5 to about 50 weight percent based on the weight of the photoacid generator. More preferably, the organic bases are selected from the tertiary amine group consisting of triethylamine, triisobutylamine, triisooctylamine, triisodecylamine, triethanolamine, and mixtures thereof.
The photosensitive compositions comprise the photosensitive polymer which is selected from the group consisting of:
(a) a photosensitive polymer having the formula: 
xe2x80x83wherein R1 is hydrogen or alkyl group having 1 to 4 carbon atoms; y is an integer from 1 to 3; Z is hydrogen atom or methyl group; the ratio of m/(m+n) ranges from 0.05 to 0.4; the ratio of n/(m+n) ranges from 0.6 to 0.95; and the photosensitive polymer has an average molecular weight ranging from about 3,000 to about 50,000;
(b) a photosensitive polymer having the formula: 
xe2x80x83wherein R1 is hydrogen or alkyl group having 1 to 4 carbon atoms; Y is hydrogen, alkyl, alkoxy, or tert-butoxycarbonyloxyl group; y is an integer from 1 to 3; Z is hydrogen atom or methyl group; the ratio of l/(l+m+n) ranges from 0.05 to 0.4; the ratio of m/(l+m+n) ranges from 0.3 to 0.85; the ratio of n/(l+m+n) ranges from 0.1 to 0.3, and the photosensitive polymer has an average molecular weight ranging from about 3,000 to about 50,000;
(c) a photosensitive polymer having the formula: 
xe2x80x83wherein R1 is hydrogen or alkyl group having 1 to 4 carbon atoms; R2 is hydrogen, methyl, ethyl, or tert-butyl group; y is an integer from 1 to 3; Z1 is hydrogen atom or methyl group; Z2 is hydrogen or methyl group; the ratio of l/(l+m+n) ranges from 0.05 to 0.4; the ratio of m/(l+m+n) ranges from 0.3 to 0.85; and the ratio of n/(l+m+n) ranges from 0.1 to 0.3; and the photosensitive polymer has an average molecular weight ranging from about 3,000 to about 50,000;
(d) a photosensitive polymer having the formula: 
xe2x80x83wherein R1 is hydrogen or alkyl group having 1 to 4 carbon atoms; y is an integer from 1 to 3; Z is hydrogen or methyl group; the ratio of m/(m+n) ranges from 0.5 to 0.7; and the ratio of n/(m+n) ranges from 0.3 to 0.5; and the photosensitive polymer has an average molecular weight from about 3,000 to about 50,000.
(e) a photosensitive polymer having the formula: 
xe2x80x83wherein R1 is hydrogen or alkyl group having 1 to 4 carbon atoms; R2 is hydrogen, methyl, ethyl, or tert-butyl group; y is an integer from 1 to 3; Z1 is hydrogen atom or methyl group; Z2 is hydrogen atom or methyl group; the ratio of l/(l+m+n) ranges from 0.3 to 0.6; the ratio of m/(l+m+n) ranges from 0.3 to 0.5; and the ratio of n/(l+m+n) ranges from 0.1 to 0.4, and the photosensitive polymer has an average molecular weight of 3,000-50,000; and
(f) a photosensitive polymer having the formula: 
xe2x80x83wherein R1 is hydrogen or alkyl group having 1 to 4 carbon atoms; R2 is hydrogen, hydroxyl, carboxyl, or tert-butyl ester group; y is an integer from 1 to 3; Z is hydrogen or methyl group; the ratio of l/(l+m+n) ranges from 0.3 to 0.6; the ratio of m/(l+m+n) ranges from 0.3 to 0.5; the ratio of n/(l+m+n) ranges from 0.1 to 0.4; and the photosensitive polymer has average molecular weight of 3,000-50,000.
Monomers or polymers which consist the photosensitive polymer according to the present invention can be easily prepared as described in the following examples.
The following examples are set forth for illustrating the invention, and are not to be interpreted as limiting thereof.